Targeted micromolecular pore throat dredging agent and preparation method thereof

Abstract

The invention relates to the technical field of oil exploitation aids, and particularly discloses a targeted micromolecular pore throat dredging agent and a preparation method thereof. The targeted micromolecular pore throat dredging agent is prepared from the following raw materials: a micromolecular active skeleton, a targeted recognition adsorbent, modified nano silicon dioxide, a modified beta-cyclodextrin derivative, a polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer, an antioxidant, a preservative and deionized water, the micromolecular active skeleton is prepared by polycondensation reaction of polycarboxylic acid and sulfur-containing active monomers; the modified nano silicon dioxide is obtained by grafting an oleophylic and hydrophobic block polymer on the surface of nano silicon dioxide; the modified beta-cyclodextrin derivative is prepared from beta-cyclodextrin, ethylenediamine and epoxy chloropropane through a grafting reaction. The dredging agent provided by the invention has a relatively high penetration rate for a micro-pore throat, and has relatively high adsorption selectivity for target blockages, so that the permeability recovery rate of a treated reservoir can be improved.

Description

Technical Field

[0001] This application relates to the technical field of petroleum extraction additives, and more specifically, to a targeted small molecule pore throat unblocking agent and its preparation method. Background Technology

[0002] In the development of low-permeability, ultra-low-permeability oil and gas reservoirs, as well as unconventional oil and gas reservoirs such as coalbed methane and shale gas, pore throats, as the core channels for oil and gas seepage, directly determine the reservoir's seepage capacity and oil and gas production. Due to the complex geological conditions of oil and gas reservoirs, the fluid-rock interaction during long-term development, and secondary damage caused by operations such as fracturing, pore throats are easily blocked by crude oil asphalt deposits, inorganic scale (such as calcium carbonate and barium sulfate), clay particle agglomerations, and other substances, leading to obstructed seepage channels, reduced production per well, and even premature entry of some reservoirs into an inefficient development stage. Pore throat unblocking agents, as key chemical agents for restoring reservoir seepage capacity, reconstruct oil and gas flow paths by dissolving, dispersing, or stripping blockages within the pore throats, and have become one of the core technical means for enhancing production in low-yield and inefficient oil and gas reservoirs and for the secondary development of old wells.

[0003] Existing pore-throat unclogging agents are mainly divided into three categories: inorganic acids, polymers, and surfactant blends. Inorganic acid unclogging agents, with hydrochloric acid and hydrofluoric acid as main components, dissolve inorganic scale blockages through acid-base reactions. Polymer unclogging agents rely on the dispersing and bridging effects of long molecular chains to peel off and suspend particulate blockages. Surfactant blends, on the other hand, reduce the interfacial tension between oil, water, and rock, helping to disperse organic deposits and improve fluid flow characteristics. Furthermore, some improved products attempt to address multiple blockages by combining different functional components, but their core operating principles remain within the framework of the aforementioned three categories.

[0004] However, existing pore-throat unclogging agents are limited by defects in molecular structure design and functional mechanisms, generally suffering from low penetration rates in micropores and throats and insufficient targeted recognition of blockages. On the one hand, polymer-based unclogging agents typically have molecular weights above 5000 Da, making them too large to penetrate micropores and throats ≤50 nm in low-permeability / ultra-low-permeability reservoirs, thus failing to reach deep blockages and resulting in generally low penetration rates. On the other hand, unclogging agents composed of inorganic acids and surfactants lack specific recognition groups for blockages, exhibiting insufficient adsorption selectivity for target blockages such as asphaltene and inorganic scale, and tend to diffuse indiscriminately in the reservoir, leading to both agent waste and potential ineffective erosion of the reservoir matrix. The combination of these two problems directly results in a permeability recovery rate of less than 65% after treatment with existing unclogging agents, failing to achieve the ideal effect for industrial applications and failing to meet the needs of efficient development of low-permeability / ultra-low-permeability and unconventional oil and gas reservoirs. Summary of the Invention

[0005] In order to enhance the unblocking effect of pore throat unblocking agents on the core channels of oil and gas seepage, and thus improve the permeability recovery rate of reservoirs after pore throat unblocking agent treatment, this application provides a targeted small molecule pore throat unblocking agent and its preparation method.

[0006] This application provides a targeted small molecule pore-throat unblocking agent and its preparation method, which adopts the following technical solution: A targeted small molecule pore-throat unblocking agent, comprising the following raw materials in parts by weight: 30-50 parts of small molecule active skeleton, 8-15 parts of targeted recognition adsorbent, 2-5 parts of modified nano silica, 3-8 parts of modified β-cyclodextrin derivative, 1-3 parts of polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer, 0.1-0.5 parts of antioxidant, 0.2-0.6 parts of preservative and 15-25 parts of deionized water; The small molecule active framework is prepared by polycondensation reaction of polycarboxylic acids and sulfur-containing active monomers; The targeted adsorbent comprises a mixture of hydrophobic alkylamines and chelated phosphonates; The modified nano-silica is obtained by grafting an oleophilic and hydrophobic block polymer onto the surface of nano-silica; The modified β-cyclodextrin derivative was prepared by grafting β-cyclodextrin with ethylenediamine and epichlorohydrin.

[0007] By adopting the above technical solution, this application addresses the shortcomings of existing polymer-based drain cleaners, which suffer from low penetration rates in micropores ≤50nm due to their large molecular size (≥5000 Da). The innovative combination of core components solves the penetration problem at the molecular level. The formulation uses a small-molecule active framework formed by the condensation of polycarboxylic acids and sulfur-containing active monomers. Through precise reaction control, this framework achieves a molecular weight ≤1000 Da and a particle size ≤5nm, with a molecular size less than 1 / 5 that of traditional polymer drain cleaners. This allows it to freely penetrate micropores ≤50nm in low-permeability / ultra-low-permeability reservoirs, completely solving the industry pain point of "deep blockages being unreachable." Simultaneously, modified nano-silica, after grafting with oleophilic and hydrophobic block polymers, forms a "nanoparticle-guided + small-molecule-followed" penetration system. Its 20-30nm particle size establishes penetration channels in the pores, further reducing the seepage resistance of the small-molecule active framework and effectively improving the penetration rate of micropores, thereby increasing the permeability recovery rate of the reservoir after drain cleaner treatment.

[0008] To address the shortcomings of existing inorganic acid and surfactant-based decontaminant agents, which lack specific recognition groups and exhibit insufficient adsorption selectivity, this technical solution constructs a dual-targeting system consisting of a "targeted recognition adsorbent + modified β-cyclodextrin derivative," achieving precise identification and adsorption of blockages. In the targeted recognition adsorbent, the hydrophobic alkylamine can form hydrophobic associations with organic blockages such as asphaltene, while the chelated phosphonate can react with Ca in inorganic scale. 2+ Mg 2+ Stable chelates are formed; the hydrophobic cavity of the modified β-cyclodextrin derivative can encapsulate organic blockage molecules, while the amino chelating group enhances the ability to capture inorganic ions. The synergistic effect of the two greatly improves the adsorption selectivity, effectively avoiding waste and matrix erosion caused by the indiscriminate diffusion of the agent in the reservoir.

[0009] The aforementioned unblocking agent achieves comprehensive optimization of "penetration-identification-unblocking" through functional synergy among its components. The polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer, acting as a dispersant and stabilizer, inhibits the aggregation of small-molecule active frameworks and nanoparticles, ensuring that the particle size remains ≤5nm in high-salt environments, further guaranteeing penetration stability. Antioxidants and preservatives extend the product's shelf life in high-temperature and high-salt formation environments, preventing functional component degradation and failure. This formulation design effectively improves the reservoir permeability recovery rate after unblocking agent treatment, while controlling the reservoir matrix erosion rate to ≤3%, perfectly meeting the development needs of low-permeability / ultra-low-permeability and unconventional oil and gas reservoirs. This solution overcomes the molecular-scale limitations of traditional unblocking agents' "difficult penetration" and solves the functional mechanism defects of "poor targeting," providing an efficient and reliable solution for enhancing the production of low-yield and inefficient oil and gas reservoirs.

[0010] Optionally, the small molecule active framework is prepared using the following method: A mixture of polycarboxylic acid, sulfur-containing active monomer, and deionized water was added, along with an acidic catalyst. The mixture was heated to 80-90℃ and stirred at 100-120 r / min for 3-4 h to obtain a small molecule active framework.

[0011] By adopting the above technical solution and controlling process parameters, precise regulation of molecular chains is achieved. Compared with existing small molecule preparation methods that lack clear reaction control, this solution can ensure that the molecular weight of the product is stably controlled within ≤1000 Da, avoiding excessive polymerization of molecular chains due to fluctuations in reaction parameters. This ensures the stability of the penetration performance of the small molecule active framework and provides process support for the consistency of subsequent unblocking effects.

[0012] Optionally, the polycarboxylic acid is selected from citric acid and aminotrimethylenephosphonic acid; the sulfur-containing active monomer is selected from mercaptoacetic acid and 2-mercaptopropionic acid.

[0013] By adopting the above technical solution, polycarboxylic acids such as citric acid and aminotrimethylene phosphonic acid possess multi-carboxyl / phosphonic acid group structures, which can enhance their chelation ability with inorganic scale; sulfur-containing active monomers such as mercaptoacetic acid and 2-mercaptopropionic acid can improve the dispersion effect on organic blockages. Compared with the single type of active raw materials in the existing technology, this solution, through the selection and adaptation of different functional monomers, can flexibly adjust the raw material combination for different blockage types (mainly organic deposits / mainly inorganic scale), broadening the application scenarios of the product and improving the practicality of the technical solution.

[0014] Optionally, the mass ratio of the polycarboxylic acid, sulfur-containing active monomer and deionized water is (2-3):1:(1.5-2.5).

[0015] Optionally, the acidic catalyst is sulfuric acid or phosphoric acid, and the amount of acidic catalyst added is 0.5%-1% of the total mass of the polycarboxylic acid and sulfur-containing active monomer.

[0016] Optionally, the modified nano-silica is prepared by the following method: A1. Mix nano-silica with hydrochloric acid solution at a mass ratio of 1:(8-12), and stir at 60-70℃ for 2-3 hours to obtain an activated modified nano-silica dispersion; the mass concentration of the hydrochloric acid solution is 5%-8%; A2. Mix the activated modified nano silica dispersion, polymethyl methacrylate-polyethylene glycol block copolymer and KH-570 coupling agent, heat to 55-65℃ and stir for 6-8 hours. After the reaction is completed, centrifuge and wash with deionized water 3-4 times. Dry under vacuum at 80-90℃ for 5-7 hours to obtain modified nano silica.

[0017] By employing the above technical solution, step A1, which activates the nano-silica with hydrochloric acid solution, removes surface impurities and introduces hydroxyl active sites, providing sufficient binding sites for subsequent grafting reactions. Step A2, in which the reaction system of activated nano-silica, block polymer, and KH-570 coupling agent is activated, ensures that the grafting rate of the block polymer on the nanoparticle surface remains stable. Compared to the simple mixing of nanoparticles in existing technologies, the modification process in this solution makes the oleophilic and hydrophobic block structure of the nano-silica more stable, allowing it to continuously play a "guide" role in the pore throat, thereby significantly improving penetration efficiency.

[0018] Optionally, the modified β-cyclodextrin derivative is prepared by the following method: B1. Dissolve β-cyclodextrin in deionized water to prepare a β-cyclodextrin aqueous solution with a mass fraction of 15%-20%. Add sodium hydroxide to adjust the pH value to 11-12, heat to 40-50℃ and stir for 1-2 hours to obtain an activated β-cyclodextrin solution. B2. Ethylenediamine and epichlorohydrin were added sequentially to the activated β-cyclodextrin solution, and then the temperature was raised to 60-70℃. The mixture was stirred at 80-100 r / min for 5-6 h. After the reaction was completed, the pH of the reaction solution was adjusted to 7-8 with hydrochloric acid. Then, 3-5 times the volume of anhydrous ethanol was added to precipitate the product. After standing for 2-3 h, the precipitate was collected by filtration. The precipitate was dissolved in deionized water and dialyzed for 48-72 h. The molecular weight cutoff of the dialysis bag was 3000 Da. Finally, the dialysate was freeze-dried to obtain the modified β-cyclodextrin derivative.

[0019] By adopting the above technical solution and through precise activation and purification processes, its dual-targeting function is enhanced. In synergy with the targeted recognition adsorbent, it effectively improves the adsorption selectivity for target blockages and further enhances the targeted unblocking effect.

[0020] Optionally, in step B2, ethylenediamine and epichlorohydrin are added sequentially to the activated β-cyclodextrin solution at a mass ratio of β-cyclodextrin: ethylenediamine: epichlorohydrin = 5: (1.5-2.5): (2-3).

[0021] Optionally, the mass ratio of hydrophobic alkylamine to chelated phosphonate in the targeted recognition adsorbent is 1:(1.2-1.8); the hydrophobic alkylamine is selected from any one of dodecylamine and hexadecylamine, and the chelated phosphonate is selected from any one of hydroxyethylidene diphosphonate and aminotrimethylene phosphonate.

[0022] Secondly, this application provides a method for preparing a targeted small molecule pore-throat unblocking agent, which adopts the following technical solution: A method for preparing a targeted small molecule pore-throat unblocking agent includes the following steps: S1. Mix the small molecule active framework and the targeted recognition adsorbent, add 2%-4% of KH-602 coupling agent by mass of the total system, and stir at 40-50℃ for 2-3 hours to obtain the premix. S2. Add modified nano-silica, modified β-cyclodextrin derivative and deionized water to the premix in sequence, and ultrasonically disperse for 25-30 min. Then add polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer and stir for 1-2 h. Then add antioxidant and preservative and mature for 12-15 h to obtain targeted small molecule pore throat unclogging agent.

[0023] By employing the above technical solution, the preparation method achieves the orderly combination of various functional components. The addition of the coupling agent in step S1 enables the target group to form covalent bonds with the small molecule backbone, avoiding the target site detachment problem caused by physical compounding in existing technologies. The ultrasonic dispersion process in step S2 ensures uniform dispersion of nanoparticles and β-cyclodextrin derivatives, preventing agglomeration from affecting penetration. Subsequent filtration, concentration, and aging processes remove impurities and stabilize product performance. This preparation method has a clear process flow and controllable parameters, ensuring consistent product performance in batch production and providing reliable process assurance for industrial applications.

[0024] In summary, this application has the following beneficial effects: 1. This application effectively solves the problem of low penetration rate of existing pore throat unclogging agents for micropores and throats. Traditional polymer-based unclogging agents have large molecular weights and sizes, making it difficult to penetrate micropore throats ≤50nm in low-permeability / ultra-low-permeability reservoirs, and deep blockages cannot be reached. This application innovatively combines core components, using polycarboxylic acids and sulfur-containing active monomers to form a small-molecule active framework. The reaction is precisely controlled to achieve a molecular weight ≤1000Da and a particle size ≤5nm, which is less than 1 / 5 the molecular size of traditional polymer unclogging agents, allowing them to freely penetrate micropore throats. At the same time, modified nano-silica, after grafting modification with oleophilic and hydrophobic block polymers, forms a "nanoparticle-guided + small-molecule-followed" permeation system. The 20-30nm particle size establishes permeation channels, reduces the seepage resistance of the small-molecule active framework, significantly improves the penetration rate of micropore throats, and thus improves the permeability recovery rate of the reservoir after unclogging agent treatment.

[0025] 2. This application successfully overcomes the shortcomings of existing pore-throat unclogging agents in their insufficient targeted recognition ability for blockages. Existing unclogging agents, which are a combination of inorganic acids and surfactants, lack specific recognition groups, resulting in insufficient adsorption selectivity for target blockages. They tend to diffuse indiscriminately in the reservoir, leading to agent waste and ineffective erosion of the reservoir matrix. This application constructs a dual-targeting system of "targeted recognition adsorbent + modified β-cyclodextrin derivative". In the targeted recognition adsorbent, the hydrophobic alkylamine forms a hydrophobic association with organic blockages such as asphaltene, while the chelated phosphonate reacts with Ca in inorganic scale. 2+ Mg 2+ It forms stable chelates; the hydrophobic cavity of the modified β-cyclodextrin derivative encapsulates organic blockage molecules, and the amino chelating groups enhance the ability to capture inorganic ions. The two work synergistically to greatly improve adsorption selectivity and effectively avoid reagent waste and matrix erosion.

[0026] 3. The preparation method of this application ensures stable product performance and solves the problem of unstable performance of existing drain cleaners due to preparation process issues. Traditional small molecule preparation methods lack clear reaction control, which easily leads to excessive polymerization of product molecular chains, affecting penetration performance. The small molecule active skeleton preparation of this application ensures that the molecular weight of the product is stably controlled within ≤1000 Da through precise control of process parameters, ensuring stable penetration performance. In the overall preparation, the addition of a coupling agent in step S1 enables the target group to form a covalent bond with the small molecule skeleton, preventing the target site from falling off; the ultrasonic dispersion process in step S2 ensures that the nanoparticles and β-cyclodextrin derivatives are uniformly dispersed, preventing agglomeration from affecting penetration; subsequent filtration, concentration, and aging processes remove impurities and stabilize product performance. The process is clear and the parameters are controllable, ensuring the consistency of product performance in batch production and providing reliable process assurance for industrial applications. Detailed Implementation

[0027] The present application will be further described in detail below with reference to the embodiments.

[0028] Preparation examples of small molecule active frameworks Preparation Example 1 The small molecule active framework was prepared using the following method: Mix 20 kg of citric acid, 10 kg of mercaptoacetic acid and 15 kg of deionized water, add 0.15 kg of 85% sulfuric acid, heat to 80 °C, and stir at 100 r / min for 3 h to obtain a small molecule active skeleton.

[0029] Preparation Example 2 The small molecule active framework was prepared using the following method: Mix 25 kg of citric acid, 10 kg of mercaptoacetic acid and 20 kg of deionized water, add 0.28 kg of sulfuric acid with a mass concentration of 85%, heat to 85 °C, and stir at 110 r / min for 3.5 h to obtain a small molecule active skeleton.

[0030] Preparation Example 3 The small molecule active framework was prepared using the following method: 30 kg of aminotrimethylenephosphonic acid, 10 kg of 2-mercaptopropionic acid and 25 kg of deionized water were mixed, 0.4 kg of phosphoric acid was added, the mixture was heated to 90 °C and stirred at 120 r / min for 4 h to obtain a small molecule active skeleton.

[0031] Preparation example of modified nano silica Preparation Example 4 Modified nano-silica was prepared using the following method: A1. Nano-silica and hydrochloric acid solution were mixed at a mass ratio of 1:8 and stirred at 60℃ for 3 hours to obtain an activated and modified nano-silica dispersion; the mass concentration of the hydrochloric acid solution was 5%. A2. The activated modified nano silica dispersion, polymethyl methacrylate-polyethylene glycol block copolymer and KH-570 coupling agent are mixed at a mass ratio of 100:8:1.5, heated to 55℃ and stirred for 6 hours. After the reaction is completed, the mixture is centrifuged, washed 3-4 times with deionized water, and dried under vacuum at 80℃ for 5 hours to obtain modified nano silica.

[0032] Preparation Example 5 Modified nano-silica was prepared using the following method: A1. Nano-silica and hydrochloric acid solution were mixed at a mass ratio of 1:10 and activated by stirring at 65°C for 2.5 h to obtain an activated modified nano-silica dispersion; the mass concentration of the hydrochloric acid solution was 6%. A2. The activated modified nano silica dispersion, polymethyl methacrylate-polyethylene glycol block copolymer and KH-570 coupling agent are mixed in a mass ratio of 100:10:2, heated to 60℃ and stirred for 7h. After the reaction is completed, the mixture is centrifuged, washed 3-4 times with deionized water, and vacuum dried at 85℃ for 6h to obtain modified nano silica.

[0033] Preparation Example 6 Modified nano-silica was prepared using the following method: A1. Nano-silica and hydrochloric acid solution were mixed at a mass ratio of 1:12 and stirred at 70°C for 2 hours to obtain an activated and modified nano-silica dispersion; the mass concentration of the hydrochloric acid solution was 8%. A2. The activated modified nano silica dispersion, polymethyl methacrylate-polyethylene glycol block copolymer and KH-570 coupling agent were mixed at a mass ratio of 100:12:2.5, heated to 65℃ and stirred for 8 hours. After the reaction was completed, the mixture was centrifuged, washed 3-4 times with deionized water, and dried under vacuum at 90℃ for 7 hours to obtain modified nano silica.

[0034] Preparation example of modified β-cyclodextrin derivatives Preparation Example 7 Modified β-cyclodextrin derivatives were prepared using the following method: B1. Dissolve β-cyclodextrin in deionized water to prepare a 15% (w / w) β-cyclodextrin aqueous solution. Add sodium hydroxide to adjust the pH to 11, heat to 40℃ and stir for 1 hour to obtain an activated β-cyclodextrin solution. B2. Ethylenediamine and epichlorohydrin were added sequentially to the activated β-cyclodextrin solution, with a mass ratio of β-cyclodextrin, ethylenediamine, and epichlorohydrin of 5:2:3. The mixture was then heated to 60°C and stirred at 80 r / min for 5 h. After the reaction was completed, the pH of the reaction solution was adjusted to 7 with hydrochloric acid. Subsequently, three volumes of anhydrous ethanol were added to precipitate the product. After standing for 2 h, the precipitate was collected by filtration. The precipitate was dissolved in deionized water and dialyzed for 48 h. The molecular weight cutoff of the dialysis bag was 3000 Da. Finally, the dialysate was freeze-dried to obtain the modified β-cyclodextrin derivative.

[0035] Preparation Example 8 Modified β-cyclodextrin derivatives were prepared using the following method: B1. Dissolve β-cyclodextrin in deionized water to prepare an 18% (w / w) β-cyclodextrin aqueous solution. Add sodium hydroxide to adjust the pH to 11.5, heat to 45°C and stir for 1.5 h to obtain an activated β-cyclodextrin solution. B2. Ethylenediamine and epichlorohydrin were added sequentially to the activated β-cyclodextrin solution, with a mass ratio of β-cyclodextrin, ethylenediamine, and epichlorohydrin of 5:1.5:2.5. The mixture was then heated to 65°C and stirred at 90 r / min for 5.5 h. After the reaction was completed, the pH of the reaction solution was adjusted to 7.5 with hydrochloric acid. Subsequently, four volumes of anhydrous ethanol were added to precipitate the product. After standing for 2.5 h, the precipitate was collected by filtration. The precipitate was dissolved in deionized water and dialyzed for 60 h. The molecular weight cutoff of the dialysis bag was 3000 Da. Finally, the dialysate was freeze-dried to obtain the modified β-cyclodextrin derivative.

[0036] Preparation Example 9 Modified β-cyclodextrin derivatives were prepared using the following method: B1. Dissolve β-cyclodextrin in deionized water to prepare a 20% β-cyclodextrin aqueous solution. Add sodium hydroxide to adjust the pH to 12, heat to 50℃ and stir for 2 hours to activate the solution and obtain an activated β-cyclodextrin solution. B2. Ethylenediamine and epichlorohydrin were added sequentially to the activated β-cyclodextrin solution, with a mass ratio of β-cyclodextrin, ethylenediamine, and epichlorohydrin of 5:2.5:2. The mixture was then heated to 70°C and stirred at 100 r / min for 6 h. After the reaction was completed, the pH of the reaction solution was adjusted to 8 with hydrochloric acid, followed by the addition of 5 times the volume of anhydrous ethanol for precipitation. After standing for 3 h, the precipitate was collected by filtration. The precipitate was dissolved in deionized water and dialyzed for 72 h. The molecular weight cutoff of the dialysis bag was 3000 Da. Finally, the dialysate was freeze-dried to obtain the modified β-cyclodextrin derivative.

[0037] Example Example 1 A targeted small molecule pore-throat unblocking agent, the raw material components and formulations of which are shown in Table 1, wherein the small molecule active skeleton is selected from the small molecule active skeleton prepared in Preparation Example 1; the targeted recognition adsorbent includes a mixture of dodecylamine and hydroxyethylidene diphosphonate in a ratio of 1:1.2; the modified nano silica is selected from the modified nano silica prepared in Preparation Example 4; the modified β-cyclodextrin derivative is selected from the modified β-cyclodextrin derivative prepared in Preparation Example 7; the antioxidant is di-tert-butyl-p-cresol; and the preservative is isothiazolinone.

[0038] A method for preparing a targeted small molecule pore-throat unblocking agent includes the following steps: S1. Mix the small molecule active framework and the targeted recognition adsorbent, add 2% KH-602 coupling agent of the total system mass, and stir at 40℃ for 2h to obtain the premix. S2. Add modified nano-silica, modified β-cyclodextrin derivative and deionized water to the premix in sequence, disperse by ultrasonication for 25 min, then add polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer and stir for 1 h; then add antioxidant and preservative and mature for 12 h to obtain targeted small molecule pore throat unclogging agent.

[0039] Example 2 A targeted small molecule pore-throat unblocking agent, the raw material components and formulations of which are shown in Table 1, wherein the small molecule active skeleton is selected from the small molecule active skeleton prepared in Preparation Example 2; the targeted recognition adsorbent includes a mixture of hexadecylamine and aminotrimethylene phosphonate in a ratio of 1:1.5; the modified nano silica is selected from the modified nano silica prepared in Preparation Example 5; the modified β-cyclodextrin derivative is selected from the modified β-cyclodextrin derivative prepared in Preparation Example 8; the antioxidant is di-tert-butyl-p-cresol; and the preservative is isothiazolinone.

[0040] A method for preparing a targeted small molecule pore-throat unblocking agent includes the following steps: S1. Mix the small molecule active framework and the targeted recognition adsorbent, add 3% of KH-602 coupling agent by mass of the total system, and stir at 45℃ for 2.5h to obtain the premix. S2. Modified nano-silica, modified β-cyclodextrin derivative and deionized water are added to the premix in sequence, and ultrasonically dispersed for 28 min. Then, polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer is added and stirred for 1.5 h. Then, antioxidant and preservative are added and matured for 14 h to obtain a targeted small molecule pore throat unclogging agent.

[0041] Example 3 A targeted small molecule pore-throat unblocking agent, the raw material components and formulations of which are shown in Table 1, wherein the small molecule active skeleton is selected from the small molecule active skeleton prepared in Preparation Example 3; the targeted recognition adsorbent includes a mixture of hexadecylamine and aminotrimethylene phosphonate in a ratio of 1:1.8; the modified nano silica is selected from the modified nano silica prepared in Preparation Example 6; the modified β-cyclodextrin derivative is selected from the modified β-cyclodextrin derivative prepared in Preparation Example 9; the antioxidant is di-tert-butyl-p-cresol; and the preservative is isothiazolinone.

[0042] A method for preparing a targeted small molecule pore-throat unblocking agent includes the following steps: S1. Mix the small molecule active framework and the targeted recognition adsorbent, add 4% KH-602 coupling agent of the total system mass, and stir at 50℃ for 3h to obtain the premix. S2. Add modified nano-silica, modified β-cyclodextrin derivative and deionized water to the premix in sequence, disperse by ultrasonication for 30 min, then add polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer and stir for 2 h; then add antioxidant and preservative and mature for 15 h to obtain targeted small molecule pore throat unclogging agent.

[0043] Table 1. Raw material components and proportions (kg) of the pore-throat unclogging agents in Examples 1-3

[0044] Example 4 A targeted small molecule pore-throat unblocking agent, differing from Example 2 in that, in this example, the small molecule active skeleton is selected from the small molecule active skeleton prepared in Preparation Example 3; the targeted recognition adsorbent comprises a mixture of hexadecylamine and aminotrimethylene phosphonate in a ratio of 1:1.8; the modified nano silica is selected from the modified nano silica prepared in Preparation Example 6; and the modified β-cyclodextrin derivative is selected from the modified β-cyclodextrin derivative prepared in Preparation Example 9.

[0045] Example 5 A targeted small molecule pore-throat unblocking agent, which differs from Example 2 in that, in this example, the small molecule active skeleton is selected from the small molecule active skeleton prepared in Preparation Example 1; the targeted recognition adsorbent includes a mixture of hexadecylamine and aminotrimethylene phosphonate in a ratio of 1:1.2; the modified nano silica is selected from the modified nano silica prepared in Preparation Example 4; and the modified β-cyclodextrin derivative is selected from the modified β-cyclodextrin derivative prepared in Preparation Example 7.

[0046] Comparative Example Comparative Example 1 The unclogging agent was prepared according to the embodiments in the patent application document with publication number CN101362942A entitled "A Formation Unclogging Agent for Low-Permeability Reservoirs in Oilfields".

[0047] Comparative Example 2 A targeted small molecule pore-throat unblocking agent, which differs from Example 2 in that an equal amount of polyacrylic acid is used instead of the small molecule active backbone in this comparative example.

[0048] Comparative Example 3 A targeted small molecule pore-throat unblocking agent, which differs from Example 2 in that an equal amount of hexadecylamine is used instead of the targeted recognition adsorbent in this comparative example.

[0049] Comparative Example 4 A targeted small molecule pore-throat unblocking agent, which differs from Example 2 in that an equal amount of unmodified nano-silica is used instead of modified nano-silica in this comparative example.

[0050] Comparative Example 5 A targeted small molecule pore-throat unblocking agent, which differs from Example 2 in that an equal amount of β-cyclodextrin is used instead of the modified β-cyclodextrin derivative in this comparative example.

[0051] Performance testing The drain cleaners prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to performance testing, and the test results are shown in Table 2.

[0052] 1. Principle of ≤50nm Micropore Throat Penetration Rate: A polycarbonate filter membrane with a pore size of 50nm is used to simulate the micropore throat of a low-permeability reservoir. The penetration ability is calculated by detecting the concentration of active components in the filtrate. Procedure: Prepare a 20wt% unclogging agent stock solution and measure the concentration of the characteristic absorption peak C0 using a UV spectrophotometer; add 10mL of the stock solution to the pressure chamber above the filter membrane, apply a constant pressure of 0.3MPa, and collect all the filtrate below; measure the concentration of the characteristic peak C1 of the filtrate, and the penetration rate = (C1 / C0) × 100%.

[0053] 2. Targeted Adsorption Selectivity Coefficient Principle: The adsorption amounts of organic blockage material (asphaltite) and inorganic blockage material (calcium carbonate) are simultaneously detected, and the ratio reflects the targeting specificity. Procedure: Prepare simulated reservoir water (mineralization 10000 mg / L) and calcium carbonate suspensions containing 1000 mg / L asphaltite and 1000 mg / L calcium carbonate, respectively; take 50 mL of each, add 0.5 g of unclogging agent, and incubate at 35℃ with shaking for 2 h; centrifuge and collect the supernatant; determine the asphaltite concentration by high-performance liquid chromatography (HPLC) and the calcium ion concentration by EDTA titration; calculate the adsorption amount (adsorption amount = (initial concentration - equilibrium concentration) × solution volume / adsorbent mass), and the selectivity coefficient = (asphaltite adsorption amount / calcium carbonate adsorption amount) × 100%.

[0054] 3. Principle of Low-Permeability Core Permeability Recovery Rate: Simulates the entire process of reservoir blockage and unblocking, evaluating the actual unblocking effect through changes in core permeability. Procedure: Select a low-permeability core (φ25mm×50mm, initial permeability 0.5-1.0mD), vacuum-saturate it to simulate formation water, and measure the basic permeability K1 of the aqueous phase; inject a plugging fluid (asphaltite + calcium carbonate mixture) until the permeability stabilizes at K2 (blockage rate ≥70%); inject an unblocking agent at a rate of 0.5mL / min, followed by water flooding until the permeability stabilizes at K3; Recovery rate = (K3-K2) / (K1-K2)×100%.

[0055] Table 2 Detection Results

[0056] As shown in Table 2, the overall performance of Examples 1-5 is significantly superior to that of the prior art. Data shows that the penetration rate of the ≤50nm micropore throats in these examples is above 86%, the targeted adsorption selectivity coefficient exceeds 94%, and the core permeability recovery rate reaches above 86%. In contrast, the three indicators of Comparative Example 1 are only 36.3%, 62.7%, and 62.1%, respectively, a significant difference. The core reason lies in the fact that this application breaks through the structural limitations of traditional unclogging agents, using a small molecule active skeleton (molecular weight ≤1000Da, particle size ≤5nm) to solve the "difficult penetration" problem. The dual system of "targeted recognition adsorbent + modified β-cyclodextrin derivative" solves the "poor targeting" problem. The synergy of these two systems enables the unclogging agent to achieve a complete functional chain of "deep contact - precise adsorption - efficient unclogging," ultimately increasing the permeability recovery rate by more than 24 percentage points.

[0057] The difference in permeability of micropore throats highlights the value of the core components, with the synergistic effect of the small-molecule active framework and modified nano-silica being key. Example 2 showed the highest permeability (92.1%) because it used the small-molecule framework (optimal process parameters) from Example 2 and the modified nano-silica (stable grafting rate) from Example 5, forming a "nanoparticle-guided + small-molecule-followed" permeation system. In contrast, in Comparative Example 2, replacing the small-molecule framework with polyacrylic acid (molecular weight 5000-8000 Da) resulted in a sharp drop in permeability to 34.6%, confirming the limitation of traditional polymers that "too large a molecular size cannot penetrate micropore throats." Comparative Example 4, with unmodified nano-silica as a substitute, had a permeability of only 41.9% because the lack of grafted oleophilic and hydrophobic block polymers prevented the establishment of permeation channels in the pore throats, leading to easy aggregation and blockage, further highlighting the necessity of the modification process.

[0058] The fluctuations in the targeted adsorption selectivity coefficient accurately reflect the synergistic effect of the dual-targeting system. Example 2 achieved a selectivity coefficient of 98.2%, attributed to the complementary functions of the targeted recognition adsorbent (hexadecylamine: aminotrimethylene phosphonate = 1:1.5) and the modified β-cyclodextrin derivative—the former binds organic / inorganic blockages through hydrophobic association and chelation, respectively, while the latter enhances its capture ability with hydrophobic cavities and amino chelating groups. In Comparative Example 3, replacing the composite adsorbent with a single hexadecylamine resulted in a sharp drop in selectivity coefficient to 40.8%, as the lack of chelating phosphonate prevented effective binding of inorganic scale ions. In Comparative Example 5, replacing the adsorbent with unmodified β-cyclodextrin reduced the coefficient to 53.4%, as the absence of ethylenediamine grafting introduced amino groups meant that dual recognition could not be achieved solely through the cyclodextrin cavity, fully demonstrating the improved targeting function after modification.

[0059] Core permeability recovery rate, as the final performance indicator, is a comprehensive reflection of penetration and targeting performance. Example 2 showed the highest recovery rate (91.4%), perfectly matching its "highest penetration rate + highest selectivity"—the small molecule framework penetrated to deep pore throats, and the targeting system precisely adsorbed blockages while reducing reagent waste; both factors combined to efficiently remove blockages. Comparative Examples 1-5 all had recovery rates below 72%, each with its own shortcomings: Comparative Example 1 had the lowest recovery rate due to dual defects; Comparative Examples 2 / 4 suffered from insufficient penetration, failing to reach deep blockages; and Comparative Examples 3 / 5 had low unblocking efficiency due to poor targeting and ineffective reagent diffusion. This data pattern confirms the scientific validity of the "penetration-identification-unblocking" collaborative design in this application and demonstrates that only by simultaneously addressing the two core defects can a qualitative improvement in permeability recovery rate be achieved.

[0060] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A targeted small molecule pore-throat unblocking agent, characterized in that, The raw materials include the following parts by weight: 30-50 parts of small molecule active skeleton, 8-15 parts of targeted recognition adsorbent, 2-5 parts of modified nano silica, 3-8 parts of modified β-cyclodextrin derivative, 1-3 parts of polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer, 0.1-0.5 parts of antioxidant, 0.2-0.6 parts of preservative and 15-25 parts of deionized water; The small molecule active framework is prepared by polycondensation reaction of polycarboxylic acids and sulfur-containing active monomers; The targeted adsorbent comprises a mixture of hydrophobic alkylamines and chelated phosphonates; The modified nano-silica is obtained by grafting an oleophilic and hydrophobic block polymer onto the surface of nano-silica; The modified β-cyclodextrin derivative was prepared by grafting β-cyclodextrin with ethylenediamine and epichlorohydrin.

2. The targeted small molecule pore-throat unblocking agent according to claim 1, characterized in that, The small molecule active framework was prepared using the following method: A mixture of polycarboxylic acid, sulfur-containing active monomer, and deionized water was added, along with an acidic catalyst. The mixture was heated to 80-90℃ and stirred at 100-120 r / min for 3-4 h to obtain a small molecule active framework.

3. The targeted small molecule pore-throat unblocking agent according to claim 2, characterized in that: The polycarboxylic acid is selected from citric acid and aminotrimethylenephosphonic acid; the sulfur-containing active monomer is selected from mercaptoacetic acid and 2-mercaptopropionic acid.

4. The targeted small molecule pore-throat unblocking agent according to claim 3, characterized in that: The mass ratio of the polycarboxylic acid, sulfur-containing active monomer, and deionized water is (2-3):1:(1.5-2.5).

5. The targeted small molecule pore-throat unblocking agent according to claim 4, characterized in that: The acidic catalyst is sulfuric acid or phosphoric acid, and the amount of acidic catalyst added is 0.5%-1% of the total mass of polycarboxylic acids and sulfur-containing active monomers.

6. The targeted small molecule pore-throat unblocking agent according to claim 1, characterized in that, The modified nano-silica was prepared using the following method: A1. Mix nano-silica with hydrochloric acid solution at a mass ratio of 1:(8-12), and stir at 60-70℃ for 2-3 hours to obtain an activated modified nano-silica dispersion; the mass concentration of the hydrochloric acid solution is 5%-8%; A2. Mix the activated modified nano silica dispersion, polymethyl methacrylate-polyethylene glycol block copolymer and KH-570 coupling agent, heat to 55-65℃ and stir for 6-8 hours. After the reaction is completed, centrifuge and wash with deionized water 3-4 times. Dry under vacuum at 80-90℃ for 5-7 hours to obtain modified nano silica.

7. The targeted small molecule pore-throat unblocking agent according to claim 1, characterized in that, The modified β-cyclodextrin derivative was prepared by the following method: B1. Dissolve β-cyclodextrin in deionized water to prepare a β-cyclodextrin aqueous solution with a mass fraction of 15%-20%. Add sodium hydroxide to adjust the pH value to 11-12, heat to 40-50℃ and stir for 1-2 hours to obtain an activated β-cyclodextrin solution. B2. Ethylenediamine and epichlorohydrin were added sequentially to the activated β-cyclodextrin solution, and then the temperature was raised to 60-70℃. The mixture was stirred at 80-100 r / min for 5-6 h. After the reaction was completed, the pH of the reaction solution was adjusted to 7-8 with hydrochloric acid. Then, 3-5 times the volume of anhydrous ethanol was added to precipitate the product. After standing for 2-3 h, the precipitate was collected by filtration. The precipitate was dissolved in deionized water and dialyzed for 48-72 h. The molecular weight cutoff of the dialysis bag was 3000 Da. Finally, the dialysate was freeze-dried to obtain the modified β-cyclodextrin derivative.

8. The targeted small molecule pore-throat unblocking agent according to claim 7, characterized in that: In step B2, ethylenediamine and epichlorohydrin are added sequentially to the activated β-cyclodextrin solution at a mass ratio of β-cyclodextrin: ethylenediamine: epichlorohydrin = 5: (1.5-2.5): (2-3).

9. The targeted small molecule pore-throat unblocking agent according to claim 1, characterized in that, The mass ratio of hydrophobic alkylamine to chelated phosphonate in the targeted recognition adsorbent is 1:(1.2-1.8); the hydrophobic alkylamine is selected from any one of dodecylamine and hexadecylamine, and the chelated phosphonate is selected from any one of hydroxyethylidene diphosphonate and aminotrimethylene phosphonate.

10. A method for preparing a targeted small molecule pore-throat unblocking agent according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Mix the small molecule active framework and the targeted recognition adsorbent, add 2%-4% of KH-602 coupling agent by mass of the total system, and stir at 40-50℃ for 2-3 hours to obtain the premix. S2. Add modified nano-silica, modified β-cyclodextrin derivative and deionized water to the premix in sequence, and ultrasonically disperse for 25-30 min. Then add polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer and stir for 1-2 h. Then add antioxidant and preservative and mature for 12-15 h to obtain targeted small molecule pore throat unclogging agent.

Images